Different topology of mixed valence CoIICoIII complexes with SCN anions and hydrazone–pyridine-based ligands

Abstract

Two novel mixed valence Co^IICo^III complexes [Co₄^II(SCN)₁₂(EtOH)₂Co₄^III(L1)₈] (1) and [Co^II(SCN)₂Co₂^III(L2)₄]_n (2) (HL1 = N’-(1-(pyridin-2-yl)ethylidene)nicotinohydrazide and HL2 = N’-(phenyl(pyridin-2-yl)methylene)isonicotinohydrazide) have been synthesized and structurally characterized by the single crystal X-ray crystallography. In both cases, the deprotonated ligands HL1 and HL2 behave as chelating species toward Co^III, further connecting Co^II fragments through the nicotine pyridine donors. A different topology is observed in the solid state of these complexes, complex 1 being an octanuclear cyclic species, while 2 is a 1D coordination polymer. The DFT calculations followed by the topological analysis of the electron density distribution have shown the existence of interesting non-covalent S···π-system interactions in 1. The CSD database search for similar supramolecular motif involving NCS anion has shown that the number and strength of S···π interactions depend both on acidity of metal cation and number aromatic systems in the molecular structure of ligand.